High-Resolution Optical Studies on C-Phycocyanin via Photochemical Hole Burning

We have shown that both the native C-phycocyanin and its corresponding free biline chromophore undergo reversible, low-temperature photochemistry. We attribute this photochemistry to reversible proton-transfer processes and utilize the observed photoreaction for photochemical hole burning (PHB). Using narrow-band PHB experiments, we have been able to perform high-resolution optical studies and show that the protein-chromophore assembly forms a very rigid structure. The results lead to the conclusion that the light-induced proton transfer occurs most probably in the triplet state

Quasi-degenerate self-trapping in one-dimensional charge transfer exciton

The self-trapping by the nondiagonal particle-phonon interaction between two quasi-degenerate energy levels of excitonic system, is studied. We propose this is realized in charge transfer exciton, where the directions of the polarization give the quasi-degeneracy. It is shown that this mechanism, unlike the conventional diagonal one, allows a coexistence and resonance of the free and self-trapped states even in one-dimensional systems and a quantitative theory for the optical properties (light absorption and time-resolved luminescence) of the resonating states is presented. This theory gives a consistent resolution for the long-standing puzzles in quasi-one-dimensional compound A-PMDA.Comment: accepted to Phys. Rev. Letter

Microscopic derivation of Frenkel excitons in second quantization

Starting from the microscopic hamiltonian describing free electrons in a periodic lattice, we derive the hamiltonian appropriate to Frenkel excitons. This is done through a grouping of terms different from the one leading to Wannier excitons. This grouping makes appearing the atomic states as a relevant basis to describe Frenkel excitons in the second quantization. Using them, we derive the Frenkel exciton creation operators as well as the commutators which rule these operators and which make the Frenkel excitons differing from elementary bosons. The main goal of the present paper is to provide the necessary grounds for future works on Frenkel exciton many-body effects, with the composite nature of these particles treated exactly through a procedure similar to the one we have recently developed for Wannier excitons.Comment: 16 pages, 4 figure

Optical second-harmonic effect of sol-gel inorganic-organic nanocomposites

Communications: Second-order nonlinear optically (NLO) active materials have promising technical applications in optoelectronic devices. A general problem in NLO-active polymeric systems is the decay of orientational order with time. Results are presented which show that using inorganic-organic composite materials produced by the sol-gel process as a rigid matrix for oriented ÷(2) chromophores (Figure) may provide a means of overcoming this problem

Nietzsche’s Death of God and the Slave-Revolt in Morality

None of Nietzsche’s theses stands out quite as much as his “Death of God” thesis. An argument can be made that the death of God is the result of the changes that the slave-revolt within morality bring about. Drawing on the observations that Nietzsche and scholars have made about the slaves and Christians, it is plausible that certain activities that the groups engaged in led to the unbelievability, or death, of God. The activities that will be given attention within this essay are the slave’s and Christian’s desire for progress and truth, which have negative and unintentional effects on other aspects of life, namely faith in God. The principal negative effects of progress and truth-seeking, being the death and decay of ideas and values, can be held responsible for decreasing levels of faith in God, while simultaneously being responsible for the increase of faith in science. This switching of faith, then, would be an explanation of how God’s existence has become unbelievable, ultimately resulting in what Nietzsche describes as his death

Linear and Nonlinear Light Chromophore Interactions

Polymers play an important role in the field of photochemical applications and photo-electrical applications. In this article we will focus on some typical examples of using polymers in modern technologies taken from the field of photoconductivity, photochemistry, and nonlinear optical applications. The latter field points towards a new direction, namely using polymers for optoelectronic applications. It will be shown that the technical material requirements for optoelectronic applications are rather different from the requirements which have to be fulfilled for conventional photochemistry and photophysics. It will be more and more the solid-state and semiconductor aspects which will enter the field of research, and developement and these new aspects will be as important as the aspects of conventional polymer physics

Nonequilibrium spectral diffusion due to laser heating in stimulated photon echo spectroscopy of low temperature glasses

A quantitative theory is developed, which accounts for heating artifacts in three-pulse photon echo (3PE) experiments. The heat diffusion equation is solved and the average value of the temperature in the focal volume of the laser is determined as a function of the 3PE waiting time. This temperature is used in the framework of nonequilibrium spectral diffusion theory to calculate the effective homogeneous linewidth of an ensemble of probe molecules embedded in an amorphous host. The theory fits recently observed plateaus and bumps without introducing a gap in the distribution function of flip rates of the two-level systems or any other major modification of the standard tunneling model.Comment: 10 pages, Revtex, 6 eps-figures, accepted for publication in Phys. Rev.

Non-Hermitian Localization and Population Biology

The time evolution of spatial fluctuations in inhomogeneous d-dimensional biological systems is analyzed. A single species continuous growth model, in which the population disperses via diffusion and convection is considered. Time-independent environmental heterogeneities, such as a random distribution of nutrients or sunlight are modeled by quenched disorder in the growth rate. Linearization of this model of population dynamics shows that the fastest growing localized state dominates in a time proportional to a power of the logarithm of the system size. Using an analogy with a Schrodinger equation subject to a constant imaginary vector potential, we propose a delocalization transition for the steady state of the nonlinear problem at a critical convection threshold separating localized and extended states. In the limit of high convection velocity, the linearized growth problem in $d$ dimensions exhibits singular scaling behavior described by a (d-1)-dimensional generalization of the noisy Burgers' equation, with universal singularities in the density of states associated with disorder averaged eigenvalues near the band edge in the complex plane. The Burgers mapping leads to unusual transverse spreading of convecting delocalized populations.Comment: 22 pages, 11 figure